What is the significance of adrenaline levels in daily life?

Adrenaline (Epinephrine) Levels and Their Significance in Daily Life

Adrenaline plays a critical role in daily physiological functions and stress responses, acting as both a hormone and neurotransmitter that helps mobilize energy stores in the form of glucose and free fatty acids for physical activity and recovery from metabolic challenges like hypoglycemia. 1

Physiological Role of Adrenaline

• Adrenaline functions as an important metabolic hormone that helps mobilize energy stores in preparation for physical activity or recovery from hypoglycemia 1
• Normal resting plasma adrenaline levels in healthy individuals range from <50 to approximately 1200 pmol/L under non-stressed conditions 2
• Adrenaline stimulates several metabolic processes including lipolysis, ketogenesis, thermogenesis, and glycolysis while raising plasma glucose concentrations 2
• The venous plasma adrenaline thresholds for metabolic effects are within physiological range: 410-680 pmol/L for lipolytic and thermogenic effects, and 550-1090 pmol/L for glycemic, ketogenic and glycolytic effects 2

Adrenaline Response to Different Stressors

• During exercise, adrenaline concentrations can increase 1.5 to >20 times above basal levels depending on exercise characteristics (duration and intensity) 3
• Chronic stress (as seen in severely ill patients) produces moderate elevations of plasma adrenaline levels (up to 1.37 ng/mL, approximately a fourfold increase over normal resting levels) 4
• Acute maximal stress, such as during cardiac arrest, can cause dramatic increases in plasma adrenaline reaching up to 35.9 ng/mL (a 300-fold increase over normal levels) 4
• Other stressors that trigger adrenaline release include hypoglycemia, hypoxia, and heat exposure 3

Adrenaline in Daily Stress Response

• Adrenaline is a mediator of the "fight-or-flight" response, preparing the body for immediate physical action 1
• Despite common belief, research suggests that the plasma adrenaline levels at which healthy subjects can reliably discriminate between adrenaline and saline infusions are actually higher than levels typically observed during mental stress 5
• The perception of stress symptoms is more strongly associated with subjective awareness of heart action changes than with actual plasma adrenaline levels or cardiovascular parameter changes 5
• This suggests that adrenaline release from the adrenal gland plays a relatively small role in producing the somatic symptoms commonly attributed to mental stress 5

Training Effects on Adrenaline Response

• Endurance-trained individuals demonstrate a higher adrenaline response to intense exercise at the same relative intensity compared to untrained individuals, a phenomenon called the "sports adrenal medulla" 3
• This enhanced capacity to secrete adrenaline is observed both in response to physical exercise and other stimuli such as hypoglycemia and hypoxia 3
• Recent research indicates that anaerobic-trained subjects also show this enhanced adrenaline response during supramaximal exercise 3
• Animal studies suggest that physical training can increase the capacity to secrete adrenaline through increased adrenal gland volume and adrenaline content 3

Clinical Significance of Adrenaline

• Adrenaline is particularly important for counter-regulation of hypoglycemia, especially in individuals with Type 1 diabetes who cannot produce endogenous insulin and lose their ability to secrete glucagon soon after diagnosis 1
• In medical emergencies such as anaphylaxis, adrenaline is the first-line treatment, administered at doses of 0.3-0.5 mg intramuscularly for adults 6
• During cardiac arrest, adrenaline is administered at 1 mg IV/IO every 3-5 minutes as part of advanced life support protocols 6
• For continuous infusions in shock states, adrenaline is typically started at 0.05-0.1 μg/kg/min and titrated to desired clinical effect 7

Regulatory Role in Metabolism

• While adrenaline is involved in minute-to-minute regulation of metabolic processes under conditions of daily living, it generally plays a secondary role in most physiological processes 2
• Individuals can survive without biologically active plasma adrenaline levels following bilateral adrenalectomy, suggesting its role is supportive rather than critical under normal conditions 2
• Adrenaline plays a more critical role under stressful conditions and in pathophysiological states, such as in altered glucose counter-regulation in patients with established insulin-dependent diabetes mellitus 2

Potential Adverse Effects of Elevated Adrenaline

• Excessive adrenaline levels can cause tachyarrhythmias, ectopic beats, and blood pressure fluctuations 6
• The potential toxicity from the adrenomedullary response to acute stress is further exacerbated by the parallel release of noradrenaline 4
• High-dose adrenaline administration has not shown improved survival outcomes in cardiac arrest situations compared to standard dosing 6